1. Field of Invention
This invention relates to passenger restraining seat belt retractors and more particularly to restraining seat belt retractors which retract to restraining seat belts on a single retractor shaft one over the other.
2. Prior Art
Three point passenger restraining devices consisting of lap and shoulder restraining belts are widely used as restraining systems for the purpose of restraining passengers during vehicle emergencies, such as collisions, etc. In these three point restraining devices, the useability and storeability of the restraining belts are improved by the installation of a retractor system which retracts, by means of an applied force, the portions of the restraining belt not used by the passenger and the majority of the seat belt when the passenger is not using the restraining belts.
In such three point restraining devices, the installation of a separate restraining belt retractor for each of the lap and shoulder restraining belts is considered to be the most effective method of improving the useability and storeability of the belts. However, a restraining belt retractor system which retracts both restraining belts on a single shaft one over the other without injuring the useability or storeability of the belts has been proposed.
As shown in FIGS. 1 and 2, this two belts retractor type of restraining belt retractor system is designed as follows. The lap restraining belt 10A and the shoulder restraining belt 10B are formed by a single continuous belt which is folded back through an opening 12 in a tongue plate 11. The lap restraining belt 10A and the shoulder restraining belt 10B, which is folded back through an eye in an anchor 14 fastened to the upper portion of the side wall of the vehicle 13, are rolled up together on a single retractor 15 one over the other.
The retractor 15 is fastened to the lower portion of a side wall of a vehicle 13 and is designed so that the lap restraining belt 10A and the shoulder restraining belt 10B are rolled up on a powered retractor shaft 16 one over the other. The passenger sitting in the seat 17 puts the three point restraining device into use by engaging the tongue plate 11 with the buckle 18 which is anchored at the approximate center line of the vehicle 13.
Use of such a two belts retractor type of restraining belt retractor system makes it possible to simultaneously extend both restraining belts by pulling either one of the restraining belts from the retractor 15. Furthermore, since one continuous restraining belt is folded back through the tongue plate 11, it is possible to adjust the relative length of each belt so that the lap restraining belt 10A and the shoulder restraining belt 10B are both constantly maintained at an appropriate length for use. Accordingly, such a system has offered superior useability and handling in spite of the fact that only a single retractor is employed.
In this double retractor type of retractor system, however, when one of the restraining belts is grasped and pulled out, the tension acting upon the other restraining belt is weakened. Accordingly, there is the possibility that the other restraining belt will become slack inside the retractor mechanism (as indicated by the broken line in FIG. 2). A restraining belt which has become slack inside the retractor mechanism has a deleterious effect upon the handling characteristics and restraining ability of the system. In addition, the generation of such unnecessary slack may interfere with the operation of the inertial lock mechanism which automatically stops the extension of the restraining belts during a vehicle emergency.
Accordingly, the present invention has been designed with the aforementioned facts and difficulties in mind.